(152e) Flow Assurance Studies with Multiphase Flowloop: High Viscosity Carrier Fluids and Viscous Heating in Hydrate Transporting Systems | AIChE

(152e) Flow Assurance Studies with Multiphase Flowloop: High Viscosity Carrier Fluids and Viscous Heating in Hydrate Transporting Systems


Bbosa, B. - Presenter, University of Tulsa
Over the life of a production well the GOR declines as the watercut increases. These changes result in high viscosity dispersion and even emulsions. As the flow assurance discipline shifts from preventing to managing hydrate formation, it is imperative for the flow assurance to fully evaluate the feasibility of hydrate transportability and the associated risks. Over the past four decades, tremendous work has been done towards understanding the impact of hydrate formation on flow properties. However, most of this work has been focused on low viscosity oils were flow assurance engineers used additives to improve phase dispersion and minimize agglomeration. Little efforts have been directed to high viscosity oils. These oils tend to form stable dispersion which poses two main challenges: high viscosity which may stall flow; high shear heating resulting from viscous friction and poor heat dissipation. Shear heating plays an important role in fluid flow because of the coupling between the energy and momentum equations. The generated heat leads to local temperature increase especially in the vicinity of pipe wall. This may have several consequences such as: local decrease in viscosity which may dramatically change the temperature and velocity profiles; affect precipitation and deposition of wax; affect solids concentration gradient and plugging mechanism for the case of hydrates. To this end, flow assurance engineers are pursuing use of drag reducing agent to minimize the effects of high viscosity fluids.

This paper presents preliminary work done towards understanding the shear heating phenomenon in oil transporting system. In addition to very high pressure losses, the systems are characterized by high shear heating effects. Four fluids were used to investigate this behavior and results showed that the temperature difference between the flowing fluid and the coolant in the annulus increased with fluid viscosity and shear rates.

The second part of the paper presents hydrate slurry flow with high viscosity fluids. Results showed that pressure drop and shear heating significantly increased during cooling into hydrate region. Shear heating continued to increase with increasing hydrate volume fraction (HVF). At a certain HVF, pressure losses hit a maximum and started decreasing. Shear heat was responsible for the change in pressure drop profile. This suggests that shear heating affects solid transport and deposition mechanism.

Lastly, the paper will present preliminary work towards use of additives to suppress the effects of high viscosity on oil transporting systems.